Sai Thong Resort, Koh Tao

While the nearby gulf islands of Samui and Phangan have been long-term draws for beach-loving travellers, the smaller Koh Tao has only recently emerged as one of Thailand's headline destinations. Primarily Tao is famed for its diving – shallow waters, easy currents, epic corals and whale sharks pull in the crowds – with numerous scuba-diving schools based here. But much of this small island still has a tranquil get-away-from-it-all vibe, and the pick of the places to indulge that atmosphere is the Sai Thong, the only resort on the tiny Sai Nuan beach. Sai Thong's tidy wooden fan-cooled bungalows are simply furnished and all have balconies, hammocks and private bathrooms. The owners are incredibly friendly, the food's excellent and vistas include the almost-private white sand beach and a massive boulder-strewn headland. Superb snorkelling, plenty of nice spots to lounge and an unforgettable arrival by long-tail boat complete the picture.
• saithongresort.info, no phone, rooms from 500 to 2,500 baht a night (around £11 to £55) depending on the room and season

Relax Bay, Koh Lanta

Just along the Andaman Sea coast, south of Krabi Town, the landscape turns into a mix of mangroves and beguiling islands. The largest of these is Koh Lanta, rightly famed for its nearby diving sites and its beaches, which are usually long, sweeping affairs, gently sloping into the warm Andaman Sea. One of the best is found at the suitably named Relax Bay, home to the resort of the same name, a French-owned endeavour complete with a range of secluded and comfortable wooden beachside bungalows and large tents. Relax is the kind of place where you might end up staying longer than planned, thanks to the almost homestay style of genuine and friendly service, authentic Thai food – the French menu isn't bad either – and calming, restful atmosphere.
• +66 75 684 194, relaxbay.com, rooms from £19-£98 depending on room and season

Bamboo Bungalows, Koh Phayam

The northern end of Thailand's Andaman Sea coast leads to the Burmese border and the sea-frontier town of Ranong. From here it's a two-hour boat ride to the island of Phayam, famous for its cashew nuts and superb beaches; indeed, Phayam is possibly the only place on earth where you can enjoy a full-moon beach party and an annual Miss Cashew Nut contest. Head to Ao Yai, or Big Beach, a 3km crescent of white sand on the west of Phayam where you'll find Bamboo Bungalows. There's a variety of beachside bungalows at this laid-back and engaging operation, from basic A-framed "shell-huts" to comfortable villas with contemporary Thai furnishings. There are kayaks and snorkelling equipment and the restaurant, which often bakes its own bread, is regarded as one of the best on the island. For a longer stay on Phayam, you can rent an entire house at Koh Phayam Sanctuary from just over £200 a month.
• +66 87 0701215, bamboo-bungalows.com, rooms from £4.50 to £32

Koh Yao Noi community homestay programme

Watching the sun rise, or set, over the limestone karst-filled waters of Phang Nga Bay makes for one the most stunning sights in Thailand. Located slap-bang in the middle of the bay is the island of Yao Noi, the perfect place to let the days slip away and engage in a bit of sun-gazing. The ambience on Yao Noi is decidedly soporific, with few cars and just a smattering of guesthouses, hotels and restaurants. The island is also home to an award-winning homestay programme run by local fishermen, and a chance to stay with one of the host families will give you an insight into a way of life the islanders are fiercely proud of. Your host family will also provide you with endless feasts of sumptuous seafood and take you on day trips to remote islands with secret beaches. Accommodation is basic, though spotlessly clean, and the families take turns to host guests according to a strict rota.
• +44 (0) 845 123 2844, symbiosis-travel.com/thailand, a three-night package with Symbiosis cost £235pp including boat and airport transfers and all excursions and activities

Nimmanoradee Resort, Koh Samet

The island of Samet, off Thailand's easterly coast a four-hour drive from Bangkok, is infamous as a weekend party island. But it offers far more than eating, drinking and loud music. The beaches are picture-perfect expanses of powder-white sand, with bay after bay running south along Samet's east coast. And the further south down the island you head, the quieter it becomes until you reach, right on the very southern tip, the Nimmanoradee Resort. Cute clapboard huts are scattered on rocky outcrops and amid trees, all with sea views, and a private sandy beach is a step away. There are kayaks, a swimming pool, deckchairs everywhere and the rooms are bathed in natural light with neat designer touches. Flatscreen TVs and bathtubs add extra comfort to the natural setting. Room rates on Samet tend to be much lower during the week.
• +66 38 644 2734, nimmanoradee.com, cottages sleep two from £58 a night

Sun Beach Guesthouse, Prachuap Khiri Khan

Six hours south of Bangkok down the Gulf of Thailand coast is the friendly fishing town of Prachuap Khiri Khan. Set on a gorgeous bay with a promenade-style seafront, Prachuap has never really succumbed to tourism so retains plenty of earthy Thai charm. The highlight is the nearby beach of Ao Manao, about 2km from the town (a tuk-tuk will take you there for £1), where you'll find an idyllic sweep of fine sand fringed by tall trees and lapped by calm waters. Manao (which means lime in Thai) is set on a low-key air force base, where you have to show your passport at the entrance gate. But don't let this put you off: the base helps protect the beach from developers, and is home to a small colony of cute dusky langur monkeys and dozens of cheap and excellent seafood stalls. There's nowhere to stay at Ao Manao, but the friendly Sun Beach Guesthouse on the Prachuap seafront comes with pool, sea-facing balconies and wonderful sunrises.
• +66 3260 4770, sunbeach-guesthouse.com, rooms from £15

The Mangrove, Koh Chang

In the far-flung corner of the eastern gulf coast is Koh Chang national marine park, where you'll find a smattering of 50 or so islands and islets in an area covering 650 sq km. At the centre is Koh Chang island itself, with hills 700m high, lush jungle and a run of exquisite beaches down its western shore. Tucked up among them is Bailan Bay, where you'll find the very lovely Mangrove bungalow operation amid woodland overlooking the sea. Everything at the Mangrove is very low-key and natural, with plenty of hammocks and cushion-strewn hang-out terraces around the resort area. The bungalows are wooden, fan-cooled affairs with cute furnishings and attached outdoor bathrooms. The beach can get a bit narrow at high tide, but the atmosphere of total relaxation and very affordable seclusion more than makes up for that. Add in excellent food, cold drinks and ice-cream and this is another place where you might find yourself staying longer than you intended.
• +66 9497 888, no website – see travelfish.org for details, bungalows from £17

Kantary Beach, Khao Lak

An hour or so north of Phuket, the Andaman Sea coast stretches out into a long run of perfect white sand beaches and the Khao Lak national park. There's little in the way of urban build here and really the only thing to do is relax and enjoy the sun. Of the numerous excellent mid-range and luxury resorts here, Kantary Beach is one of the best, and makes for a great choice for families, too. The contemporary designer rooms are massive – each comes with separate living area, sofa bed, mini-kitchen and balcony – but surprisingly affordable, while the 11km of palm-fringed beach the rooms look on to is perfect for luxuriant tropical lazing. The resort serves excellent seafood and Thai grub, has a kids' play area, a huge pool and also rents out kayaks and mini-catamarans to guests.
• +66 7658 4700, kantarycollection.com, rooms from £40 low season to £80 high season

OonLee Bungalows, Koh Jum

Most visitors to the Andaman Coast hub of Krabi head straight to the flesh-pot of Phi Phi or the busy beaches of Ao Nang – and have probably never even heard of the nearby island of Jum. Those who make it to Koh Jum are thankful that this somnolent, verdant isle is still off the radar. The beaches here are not the postcard-perfect sweeps of white sand you'll find elsewhere, but the charm is in the Chao Ley (Sea Gypsy) locals, the thick jungle and the quirkiness. The pick of places to stay is OonLee Bungalows, run by a Frenchwoman and her Thai husband – who also happens to be a gourmet chef and a carpenter. The gorgeous homely little bungalows that blend in with the forest and peer over the sea are a labour of love for the owners. Factor in awesome food, a welcome as friendly as you'll find anywhere, plus enough hammocks and big soft cushions for a lifetime's worth of lazing and you should be suitably bewitched.
• +66 8720 08053, kohjumoonleebungalows.com, from £13 to £87 depending on room and season

Tarutao national park bungalows

Once home to pirates and political prisoners, Tarutao, at the southern end of Thailand's Andaman coast, is now one of Thailand's best-protected national parks. The interior is filled with thick jungle and all manner of beasties, including snakes and monkeys, and the beaches are extraordinarily beautiful. In terms of places to stay and eat, this protection keeps things at a basic, though adequate, level and on all beaches the only choice is simple national park bungalows, with minimal electricity, and cold water. If you can brave these conditions, you will be amply rewarded, as stunning Tarutao is kept pretty much as nature intended.
• kotarutaothailand.com, reservations (book in advance), two-person bungalows from £11
The photo caption to this entry was amended on 17 January 2012

Andrew Spooner is the author of Footprint's Thailand Handbook (new edition out in June 2012) and associate editor of travelwireasia.com